1 Introduction
2 Research Background
3 Materials and Test Methods
3.1 Mix Design of SHCC
Type | Ida
| Cementb
| Fly-ash | Sandc
| Water | Fibre (%) | SP | VMA | AEA |
---|---|---|---|---|---|---|---|---|---|
FS-SHCC | FS2 | 392 (42.5) | 674 | 553 | 392 | 2.01 | 1.99 | 0.54 | 0.54 |
FS-SHCC | FS31 & FS32 | 392 (52.5) | 674 | 553 | 392 | 2.01 | 1.99 | 0.54 | 0.54 |
CS-SHCC | CS2 | 392 (42.5) | 674 | 553 | 392 | 2.01 | 1.99 | 0.54 | 0.54 |
FS-Mortar | FM1 | 401 (42.5) | 688 | 565 | 401 | – | – | 1.0 | – |
FS-Mortar | FM2 | 401 (52.5) | 688 | 565 | 401 | – | – | 1.0 | – |
CS-Mortar | CM1 | 401 (42.5) | 688 | 565 | 401 | – | – | 1.0 | – |
3.2 Specimen Preparation for Corrosion Testing
Type | Cover (mm) | Nr of specimens | Nr of notches/cracksa
| Deformation (mm)b
|
---|---|---|---|---|
FS32 | 15 (C15) | 3 | 1 (N1) | 0.30 |
3 | 3 @ 40 mm (N3) | 0.90 | ||
3 | 5 @ 20 mm (N5) | 1.50 | ||
25 (C25) | 3 | 1 (N1) | 0.30 | |
3 | 3 @ 40 mm (N3) | 0.90 | ||
3 | 5 @ 20 mm (N5) | 1.50 | ||
FM2 | 15 (C15) | 2 | 1 (N1) | 0.15 |
25 (C25) | 2 | 1 (N1) | 0.15 |
3.3 Method of Forming Cracks in the Specimens
3.4 Corrosion Test Setup
3.5 Method of Determining Chloride Content
4 Research Results
Id | Slump (mm) |
f
cu
(MPa) |
E-mod (GPa) |
f
u,st
(MPa) |
f
cr,st
(MPa) |
ε
u,st
(%) |
---|---|---|---|---|---|---|
FS2 | 170–200 | 25 | 14 | 2.6 | 2 | 2.2 |
FS31 & FS32 | 180–200 | 24–28 | 13–14 | 2.2–2.5 | 1.6–1.8 | 1.6–2.0 |
CS2 | 195–225 | 23 | 13 | 2.01 | 1.8 | 1.2 |
FM1 & FM2 | 200–220 | 26–31 | 15–17 | – | – | – |
CM1 | 220–225 | 27 | 17 | – | – | – |
4.1 Flexural Cracks in the R/SHCC Specimens
4.2 Corroded Depth in R/SHCC and R/Mortar Specimens
4.3 Visual Observation of Corrosion Damage
4.4 Loss of Yield Force and Pitting in Steel Bars Due to Corrosion
4.5 Chloride Content in the R/SHCC and R/Mortar Specimens
4.6 Relationship Between XRF and Chemical Total Chloride
4.7 Total and Free Chloride Content at Different Depth of Specimens
5 Discussion of Results
5.1 Influence of Chloride Content and Mass Loss of Steel in Corrosion
5.2 Effect of Cracking in Chloride Penetration
6 Conclusions
-
Average and maximum crack widths and crack spacing in the R/SHCC are smaller for larger cover depth of the steel bar. From the particular type of SHCC used in this research, it appears that a 25 mm cover depth is the threshold cover depth for limiting the crack width in R/SHCC.
-
Mass loss, pitting depth and loss of yield force are considered to be low in all specimens, despite up to 108 weeks of cyclic wetting and drying chloride exposure. After 108 weeks of such exposure, a maximum pitting depth of 1.4 mm was found in the 10 mm diameter steel bars, with the average pitting depth in the range 0.1–0.5 mm. For lower exposure durations, the average pitting depths were lower at 0.1–0.4 mm after 57 weeks, and 0.1–0.3 mm after 28 weeks of cyclic chloride exposure. This led to a maximum loss of yield force of the bars of about 17% in a CS2_C15B1 specimens.
-
In chloride-induced corrosion performed here, higher corroded depths (measured by a Coulostatic method), actual measured pitting depths, and higher loss of yield force in the steel were found in the specimens with cover depth of 15 mm than for 25 and 35 mm cover depths. No significant difference was observed in the specimens with 25 and 35 mm cover depths.
-
A significant reduction in tensile strain capacity was found for SHCC produced with coarse sand (CS2) compared with fine sand. However, there were no significant differences in the pitting depths and loss of yield force of steel in coarse sand specimens CS2 and CM1 than in fine sand specimens FS2 and FM1.
-
Free chloride content in the specimen at the level of the steel bar appears to correlate better with the corrosion damage than total chloride content. However, while the role of chloride in corrosion initiation has been studied widely, its role in corrosion propagation and corrosion rate must be investigated further.
-
The XRF method can be an alternative method for chemical testing in determining total chloride content in SHCC. Both total and free chloride content reduced with depth into the specimens and the difference between chemical total and free chloride content was found to be in the range of 5–65%, depending on the depth in the specimen.
-
The actual mass loss of steel bars is related to the corroded depths and loss of yield force of R/FS32 and R/FM2 specimens. The pitting depth in the steel bars was larger for larger average crack spacing in the R/SHCC specimens.
-
A larger number of cracks, associated with finer crack spacing, lead to significantly lower corrosion damage in R/SHCC.